1. Field of the Invention
The present invention relates to a method of manufacturing potassium cyanate. More particularly, the present invention relates to a method for producing potassium cyanate from potassium hydroxide and urea in very high yield.
2. Description of the Prior Art
Among the reactions known for the synthesis of alkali metal cyanates is the reaction between an alkali metal compound and urea. Suitable alkali metal compounds have included the carbonate, bicarbonate, hyydride, oxide, alcoholate, carbide and hydroxide compounds of the alkali metals. The reactants have been reacted either as a melt of the components or in an aqueous solution. One process (Kloepfer, U.S. Pat. No. 1,915,425) shows the production of alkali metal cyanates by the reaction of a basic alkali metal compound, such as potassium carbonate, with urea in a melt. However, it is disclosed that if an hydroxide of an alkali metal is used such as, of course, pottasium hydroxide, yields of only 10 to 30% of potassium cyanate are obtained. Yields of this order are unacceptable for the commercial production of potassium cyanate.
Another procedure for the production of alkali metal cyanates involves the reaction of an alkali metal carbonate with urea in a melt, wherein the molar amounts of urea range from 2.0 to 3.0 preferably 2.3 to 3.0 per mole of alkali metal carbonate (Horst, U.S. Pat. Nos. 2,690,956 and 2,690,957). By this procedure yields of alkali metal cyanate up to 85-90 percent are obtained. However, yields of potassium cyanate even of this order still fall short of total conversion of urea and alkali compound to potassium cyanate.
In another known procedure for manufacturing alkali metal cyanates, an alkali metal hydroxide is reacted with urea in a fluidized bed reactor wherein a mole ratio of 0.8 to 1.4 moles of urea per mole of an alkali metal hydroxide is used (Davis, U.S. Pat. No. 3,321,270). However, the yields of cyanate product in this procedure, while substantial, are not more than about 95 percent.
Still another process for the production of alkali metal cyanates involves the reaction of an alkali metal carbonate or hydroxide with urea. In this reaction the quantities of urea used range only from the stoichiometric amount (mole ratio of urea to KOH of 1.0) required to react with the alkali metal compound to 10 percent in excess of that amount. However, at these relative quantities of urea to alkali metal compound, the yields of product alkali metal cyanate obtained, while substantial, are only about 90 percent. It is further disclosed that there is no advantage to be gained by using quantities of urea over 10 percent in excess of the stoichiometric amount required to react with the alkali metal compound. This statement is in direct contrast to the process of the present invention, wherein the amounts of urea relative to alkali metal base used, achieve yields of product alkali metal cyanate is in excess of 90 percent.
Another process for the preparation of alkali metal cyanates also involves the reaction of an alkali metal compound and urea. However, because very great amounts of urea are required relative to the amount of alkali metal compound, i.e., mole ratios of urea to alkali metal compound of about 6 : 1 (Barrett and Kamlet, U.S. Pat. No. 2,899,198), the process if highly inefficient in the utilization of urea.
Other known processes for the production of alkali metal cyanates include the reaction between isohydroxyurea and an alkali metal hydroxide in a simple alcohol and the reaction between sodium and urea in a dispersion wherein N-sodiourea is first formed.
A need therefore, continues to exist for a method for producing alkali metal cyanates in high purity in yields greater than 90 percent by the direct interaction of an alkali metal hydroxide with urea.